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One option for making fusion power plants that could be competitive with other power plants operating during the 21st century is to make them large, e.g., 3 GW(electric) or more, to take advantage of the expected economies of scale. This study examines the effects on electrical utility system hardware, operations, and reliability of incorporating such large generating units. In addition, the study evaluates the use of the coproduction of hydrogen to reduce the grid-supplied electricity and offer the possibility for electrical load-following.

The estimated additional cost of electricity (COE) for a large power plant is ~5 mills/kWh. The estimated total COE for 3- to 4-GW(electric) fusion power plants lies in the range of 37 to 60 mills/kWh.

Future hydrogen costs from a variety of sources are estimated to lie in the range of 8 to 10 $/GJ, when allowance is made for some increase in natural gas price and for the possible need for greenhouse gas emission limitations.

A number of combinations of fusion plant and electrolyzer were considered, including hot electrolyzers that use heat from the fusion plant. For the optimum cases, hydrogen produced from off-peak power from a 3- to 4-GW(electric) plant is estimated to have a competitive cost. Of particular interest, the cost would also be competitive if some hydrogen were produced during on-peak electricity cost periods. Thus, for a 4-GW(electric) plant, only up to 3 GW(electric) might be supplied to the grid, and load-following would be possible, which would be a benefit to the utility system.